This may be workable if the PDP-11 simulator runs under DOS or LINUX. If it
runs under Windows, the OS will interfere with your attempts to talk
directly to I/O.
If you have a version for LINUX, you'll need one of the EPP port drivers,
but that's what I'd recommend you attempt first. EPP uses the parallel
printer port to mux and steer data into your target application. You must
understand what it does, and how slowly, ( it's more or less rate-limited to
about a 4 MB/sec transfer rate, but that's an asymptote.) If you find a way
to make it work, and it works quite straightforwardly under DOS, then you
write addresses and commands to one location mapped into the parallel data
port, 0x37C, and data to 0x37C.
The hardware will generate strobes to facilitate such transfers, so you
don't have to wiggle the strobes with software. It has a Data Strobe and an
Address strobe, provides for an interrupt if you want one, and various other
features, none of which require you use them.
Though this form of bus-isolated I/O is very tempting, it's a good idea to
keep in mind that the IC in which the printer port lives is normally a
high-pin-count device soldered to the motherboard. If you break it, you
have to use an off-motherboard circuit to provide the printer port, as well
as whatever other peripherals are lost along with it. That, these days, can
include lots of functions you'd rather not lose.
It's a good idea to isolate your circuitry from the motherboard with series
resistors, or even picofuses, and provide adequate buffering to make it safe
to use.
If you know enough about the PC and the way the simulator runs on it, you
need merely drive your indicators in a way that reflects the status of the
simulated PDP-n, hving patched your code into the simulator's primary
dispatch loop.
Dick
----- Original Message -----
From: Eros, Anthony <Anthony.Eros_at_compaq.com>
To: <classiccmp_at_classiccmp.org>
Sent: Thursday, June 08, 2000 3:44 PM
Subject: Wirin' up blinkenlights
> Here's a question for the group. I have a PC running Bob Supnik's PDP-11
> simulator and a PDP-11/45 front panel with no CPU boards. I'd like to do
> sort of a faux PDP-11/45 with this setup by somehow wiring the front panel
> up to the PC running Sim.
>
> Am I completely out of my mind, or is there even the remotest chance of
> getting something like this to work?
>
> -- Tony
>
Received on Thu Jun 08 2000 - 17:22:56 BST